The invention relates to improvements in apparatus for preparing and dispensing liquids which are used for the treatment of photosensitive materials. More particularly, the invention relates to improvements in apparatus which can be utilized to mix water or another liquid substance with at least one second substance (such as a liquid and/or a solid material which is dispersible or soluble in water or in another liquid substance) to form a mixture for the processing of exposed but undeveloped photographic films and/or for the processing of exposed but undeveloped photographic paper in a photographic processing laboratory.
If a processing laboratory is designed to consume large quantities of liquid developing materials, it is customary to supply various chemicals in highly concentrated form and to make the bath or baths (such as a developing, mixing or rinsing bath) at the locus of actual use. In many instances, chemicals which are supplied in solid form must be mixed with water to form therewith mixtures, solutions or dispersions (hereinafter called mixtures) which are ready to treat exposed but undeveloped photographic films, webs or sheets of photographic paper and/or other photosensitive materials. The concentrated substances which are to be mixed with water or with another liquid substance can be supplied in solid form (e.g., in a granular or pulverulent state) or in the form of liquids which are to be mixed with, dispersed in or dissolved in water or in another liquid substance. To this end, the photographic processing laboratories are equipped with special mixing apparatus which are designed to prepare liquids ready to contact webs, sheets, strips or other forms of photosensitive material. For example, certain known apparatus are designed to supply a mixture to one or more tanks for developing, fixing or other liquids in such a way that the respective tank or tanks receive regenerating mixtures without any interruptions as long as the developing machine is on.
In accordance with a presently known proposal, a mixing apparatus of the above outlined character is equipped with a mixing tank and a discrete storage or buffer tank. The storage tank is installed at a level below and is connected with the mixing tank. The connection is controlled by a magnetic valve in such a way that a fresh supply of mixture of water with one or more solid and/or liquid substances is caused or permitted to flow from the mixing tank into the storage tank as soon as a mixing operation in the mixing tank is completed. The valve then opens and a portion of the freshly obtained mixture is transferred into the storage tank. The latter continuously supplies the mixture to the developing machine proper, and the supply of mixture therein is continuously replenished through the magnetic valve. When the mixing tank is empty (i.e., when only the storage tank still contains a certain quantity of mixture), the magnetic valve is closed and the preparation of a fresh supply of mixture in the mixing tank is ready to take place.
Certain mixing apparatus of the above outlined character are provided with a horizontal partition which divides a vessel into a mixing tank and a storage tank, with the storage tank located at a level below and the mixing tank located at a level above the horizontal partition. The magnetic valve is designed to control the flow of mixture from the mixing tank, through an opening in the horizontal partition, and into the storage tank. Thus, the magnetic valve is in continuous contact with and is likely to be contaminated or clogged by certain constituents of the mixture, e.g., by non-dissolved solid granular and/or pulverulent particles which were to be admixed to and dissolved in water in the course of a mixing operation. This results in repeated stoppages of the apparatus and of the entire processing laboratory. Another drawback of such apparatus is that the storage tank is completely enclosed, i.e., that its interior is not accessible without at least partial dismantling of the apparatus. On the other hand, convenient access to the interior of the storage tank is desirable and advantageous, e.g., for evacuation of gathered sediments at regular or irregular intervals.
Attempts to overcome the drawbacks of the aforedescribed apparatus include the provision of two separate vessels, one of which constitutes a mixing tank and the other of which constitutes a storage tank. The two tanks are connected to each other by a hose, and the flow of mixture in the hose from the mixing tank to the storage tank is controlled by a magnetic valve. Such apparatus are rather expensive and their space requirements are much greater than those of apparatus wherein the mixing tank and the storage tank constitute portions of a single container.